Bonding apparatus, bonding system, bonding method and storage medium

ABSTRACT

There is provided a bonding apparatus for bonding substrates together, which includes: a first holding part configured to adsorptively hold a first substrate by vacuum-drawing the first substrate on a lower surface of the first substrate; a second holding part provided below the first holding part and configured to adsorptively hold a second substrate by vacuum-drawing the second substrate on an upper surface of the second substrate; a pressing member provided in the first holding part and configured to press a central portion of the first substrate; and a plurality of substrate detection parts provided in the first holding part and configured to detect a detachment of the first substrate from the first holding part.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-233985, filed on Dec. 1, 2016, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a bonding apparatus for bondingsubstrates together, a bonding system provided with the bondingapparatus, a bonding method using the bonding apparatus and anon-transitory computer-readable storage medium.

BACKGROUND

In recent years, high integration of semiconductor devices has beenadvanced. In a case where a plurality of highly integrated semiconductordevices is arranged in a horizontal plane and is connected by wires forproduction, there is a concern that the wiring length is increased, theresistance of wires is increased, and the wiring delay is large.

Under the circumstances, there has been proposed the use of athree-dimensional integration technology that three-dimensionally stackssemiconductor devices. In this three-dimensional integration technology,two semiconductor wafers (hereinafter referred to as “wafers”) arebonded through the use of, e.g., a conventional bonding system. Forexample, the bonding system includes a surface modifying apparatus formodifying a surface of a wafer to be bonded, a surface hydrophilizingapparatus for hydrophilizing the surface of the wafer modified with thesurface modifying apparatus, and a bonding apparatus for bonding thewafers whose surfaces are hydrophilized with the surface hydrophilizingapparatus. According to this bonding system, in the surface modifyingapparatus, plasma treatment is performed on the surface of the wafer tomodify the surface of the wafer. In the surface hydrophilizingapparatus, pure water is supplied to the surface of the wafer tohydrophilize the surface of the wafer. Thereafter, in the bondingapparatus, the wafers are bonded to each other by virtue of a van derWaals force and a hydrogen bond (intermolecular force).

The bonding apparatus includes an upper chuck configured to hold onewafer (hereinafter referred to as “upper wafer”) on the lower surfacethereof, a lower chuck installed under the upper chuck and configured tohold another wafer (hereinafter referred to as “lower wafer”) on theupper surface thereof, and a pressing member provided in the upper chuckand configured to press the central portion of the upper wafer. In sucha bonding apparatus, in a state in which the upper wafer held by theupper chuck and the lower wafer held by the lower chuck are disposed toface each other, the central portion of the upper wafer and the centralportion of the lower wafer are pressed and brought into contact witheach other by the pressing member, whereby the central portions arebonded to each other to form a bonding area. Thereafter, a so-calledbonding wave occurs in which the bonding area expands from the centralportion of the wafer to the outer peripheral portion thereof. Thus, theupper wafer and the lower wafer are bonded.

In order to suppress distortion of the laminated wafer after bonding, itis preferable that the bonding wave is uniformly (i.e., concentrically)expanded from the central portion of the wafer toward the outerperipheral portion thereof. However, in the bonding apparatus describedabove, the bonding wave is not monitored. Therefore, even if the bondingwave is unevenly expanded, it is not possible to grasp such an unevenexpansion. Accordingly, there is room for improvement in the waferbonding process of the related art.

SUMMARY

Some embodiments of the present disclosure provide a technique capableof inspecting a state of a bonding process of substrates andappropriately performing the bonding process.

According to one embodiment of the present disclosure, there is provideda bonding apparatus for bonding substrates together, including: a firstholding part configured to adsorptively hold a first substrate byvacuum-drawing the first substrate on a lower surface of the firstsubstrate; a second holding part provided below the first holding partand configured to adsorptively hold a second substrate by vacuum-drawingthe second substrate on an upper surface of the second substrate; apressing member provided in the first holding part and configured topress a central portion of the first substrate; and a plurality ofsubstrate detection parts provided in the first holding part andconfigured to detect a detachment of the first substrate from the firstholding part.

According to another embodiment of the present disclosure, there isprovided a bonding system provided with the bonding apparatus of claim1, which includes: a processing station provided with the bondingapparatus; and a loading/unloading station configured to hold aplurality of first substrates, a plurality of second substrates or aplurality of laminated substrates each of which is obtained by bondingthe first substrate and the second substrate, and configured to load andunload the plurality of first substrates, the plurality of secondsubstrates or the plurality of laminated substrates into and from theprocessing station, wherein the processing station includes: a surfacemodifying apparatus configured to modify a surface of the firstsubstrate or the second substrate to be bonded; a surface hydrophilizingapparatus configured to hydrophilize the surface of the first substrateor the surface of the second substrate modified by the surface modifyingapparatus; and a transfer device configured to transfer the plurality offirst substrates, the plurality of second substrates or the plurality oflaminated substrates to the surface modifying apparatus, the surfacehydrophilizing apparatus and the bonding apparatus, and wherein thebonding apparatus is configured to bond the first substrate and thesecond substrate whose surfaces are hydrophilized by the surfacehydrophilizing apparatus.

According to another embodiment of the present disclosure, there isprovided a bonding method for bonding substrates together, whichincludes: arranging a first substrate held on a lower surface of a firstholding part and a second substrate held on an upper surface of a secondholding part so as to face each other; subsequently, lowering a pressingmember provided in the first holding part and configured to press acentral portion of the first substrate, and causing the pressing memberto press and bring the central portion of the first substrate and acentral portion of the second substrate into contact with each other;and subsequently, sequentially bonding the first substrate and thesecond substrate from the central portion of the first substrate towardan outer peripheral portion of the first substrate in a state in whichthe central portion of the first substrate and the central portion ofthe second substrate are in contact with each other, wherein the bondingthe first substrate and the second substrate includes detecting adetachment of the first substrate from the first holding part andinspecting a state of a bonding process, using a plurality of substratedetection parts provided in the first holding part.

According to another embodiment of the present disclosure, there isprovided a non-transitory computer-readable storage medium storing aprogram that operates on a computer of a control part configured tocontrol a bonding apparatus so that the aforementioned bonding method isexecuted by the bonding apparatus.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the presentdisclosure, and together with the general description given above andthe detailed description of the embodiments given below, serve toexplain the principles of the present disclosure.

FIG. 1 is a plan view schematically showing a configuration of a bondingsystem according to an embodiment.

FIG. 2 is a side view schematically showing an internal configuration ofa bonding system according to an embodiment.

FIG. 3 is a side view schematically showing configurations of an upperwafer and a lower wafer.

FIG. 4 is a horizontal sectional view schematically showing aconfiguration of a bonding apparatus.

FIG. 5 is a vertical sectional view schematically showing aconfiguration of a bonding apparatus.

FIG. 6 is a vertical sectional view schematically showing configurationsof an upper chuck, an upper chuck holding part and a lower chuck.

FIG. 7 is a plan view of an upper chuck as viewed from below.

FIG. 8 is an explanatory view showing a state of expansion of a bondingarea between wafers in the related art.

FIGS. 9A and 9B are graphs showing examples of a detection result ofsensors.

FIG. 10 is a flowchart showing main steps of a wafer bonding process.

FIG. 11 is an explanatory view showing a state in which an upper waferand a lower wafer are arranged to face each other.

FIG. 12 is an explanatory view showing a state in which a centralportion of an upper wafer and a central portion of a lower wafer arepressed and brought into contact with each other.

FIG. 13 is an explanatory view showing a state in which the bonding ofan upper wafer and a lower wafer is expanded from a central portion toan outer peripheral portion.

FIG. 14 is an explanatory view showing a state in which a surface of anupper wafer and a surface of a lower wafer are brought into contact witheach other.

FIG. 15 is an explanatory view showing a state in which an upper waferand a lower wafer are bonded.

FIG. 16 is a plan view of an upper chuck, which shows an arrangement ofsensors according to another embodiment.

FIGS. 17A to 17D are plan views of an upper chuck, which showsarrangements of sensors according to other embodiments.

FIG. 18 is a vertical sectional view schematically showingconfigurations of an upper chuck, an upper chuck holding portion, and alower chuck according to another embodiment.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described below withreference to the accompanying drawings. It should be noted that thepresent disclosure is not limited by the embodiments described below. Inthe following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the presentdisclosure. However, it will be apparent to one of ordinary skill in theart that the present disclosure may be practiced without these specificdetails. In other instances, well-known methods, procedures, systems,and components have not been described in detail so as not tounnecessarily obscure aspects of the various embodiments.

1. Configuration of Bonding System

First, a configuration of a bonding system according to the presentembodiment will be described. FIG. 1 is a plan view schematicallyshowing the configuration of the bonding system 1. FIG. 2 is a side viewschematically showing an internal configuration of the bonding system 1.

In the bonding system 1, as shown in FIG. 3, for example, two wafersW_(U) and W_(L) as substrates are bonded to each other. Hereinafter, thewafer arranged at the upper side is referred to as “upper wafer W_(U)”as a first substrate, and the wafer arranged at the lower side isreferred to as “lower wafer W_(L)” as a second substrate. Furthermore, asurface of the upper wafer W_(U) to be bonded is referred to as a “frontsurface W_(U1)”, and a surface opposite to the front surface W_(U1) isreferred to as a “back surface W_(U2)”. Similarly, a surface of thelower wafer W_(L) to be bonded is referred to as a “front surfaceW_(L1)”, and a surface opposite to the front surface W_(L1) is referredto as a “back surface W_(L2)”. In the bonding system 1, the upper waferW_(U) and the lower wafer W_(L) are bonded to form a laminated waferW_(T) as a laminated substrate.

As shown in FIG. 1, the bonding system 1 includes, for example, aloading/unloading station 2 in which cassettes C_(U), C_(L) and CT eachcapable of accommodating a plurality of wafers W_(U) and W_(L) and aplurality of laminated wafers W_(T) are loaded and unloaded with respectto the outside, and a processing station 3 provided with variousprocessing apparatuses for performing predetermined processes on thewafers W_(U) and W_(L) and the laminated wafers W_(T). Theloading/unloading station 2 and the processing station 3 are integrallyconnected to each other.

In the loading/unloading station 2, there is provided a cassettemounting table 10. On the cassette mounting table 10, a plurality of,for example, four, cassette mounting plates 11 are provided. Thecassette placing plates 11 are arranged in a line along an X-direction(up-down direction in FIG. 1) which is a horizontal direction. On thecassette mounting plates 11, the cassettes C_(U), C_(L) and C_(T) can bemounted when the cassettes C_(U), C_(L) and C_(T) are loaded andunloaded with respect to the outside of the bonding system 1. In thisway, the loading/unloading station 2 is configured to hold a pluralityof upper wafers W_(U), a plurality of lower wafers W_(L) and a pluralityof laminated wafers W_(T). The number of the cassette mounting plates 11is not limited to that of the present embodiment and may be arbitrarilyset. One of the cassettes may be used for recovering abnormal wafers.That is to say, one of the cassettes may be a cassette that can separatethe wafers having an abnormality occurring when bonding the upper waferW_(U) and the lower wafer W_(L) due to various factors from other normallaminated wafers W_(T). In the present embodiment, one cassette C_(T)out of a plurality of cassettes C_(T) is used to recover abnormalwafers, and other cassettes C_(T) are used to accommodate normallaminated wafers W_(T).

In the loading/unloading station 2, a wafer transfer part 20 is providedadjacent to the cassette mounting table 10. In the wafer transfer part20, there is provided a wafer transfer device 22 movable along atransfer path 21 extending in the X-direction. The wafer transfer device22 is also movable in a vertical direction and about a vertical axis (ina 0 direction). The wafer transfer device 22 is capable of transferringthe wafers W_(U) and W_(L) and the laminated wafers W_(T) between thecassettes C_(U), C_(L) and C_(T) on the respective cassette mountingplates 11 and transition devices 50 and 51 of a third processing blockG3 of the processing station 3 to be described later.

In the processing station 3, there are provided a plurality of, forexample, three, processing blocks G1, G2 and G3 including variousdevices. For example, a first processing block G1 is provided at a frontsurface side (in the negative X-direction in FIG. 1) of the processingstation 3, and a second processing block G2 is provided at a backsurface side (in the positive X-direction in FIG. 1) of the processingstation 3. A third processing block G3 is provided at the side of theloading/unloading station 2 (in the negative Y-direction in FIG. 1) ofthe processing station 3.

For example, in the first processing block G1, a surface modifyingapparatus 30 for modifying the surfaces W_(U1) and W_(L1) of the wafersW_(U) and W_(L) is arranged. In the surface modifying apparatus 30, forexample, an oxygen gas or a nitrogen gas as a processing gas is excited,plasmarized and ionized in a depressurized atmosphere. The oxygen ionsor nitrogen ions are irradiated onto the surfaces W_(U1) and W_(L1),whereby the surfaces W_(U1) and W_(L1) are plasma-processed andmodified.

For example, in the second processing block G2, a surface hydrophilizingapparatus 40 for hydrophilizing the surfaces W_(U1) and W_(L1) of thewafers W_(U) and W_(L) and cleaning the surfaces W_(U1) and W_(L1), forexample, with pure water, and a bonding apparatus 41 for bonding thewafers W_(U) and W_(L) are arranged side by side in the named order fromthe side of the loading/unloading station 2 along the Y-direction whichis the horizontal direction. A configuration of the bonding device 41will be described later.

In the surface hydrophilizing apparatus 40, for example, pure water issupplied onto the wafers W_(U) and W_(L) while rotating the wafers W_(U)and W_(L) held by spin chucks. Then, the supplied pure water is diffusedon the surfaces W_(U1) and W_(L1) of the wafers W_(U) and W_(L), wherebythe surfaces W_(U1) and W_(L1) are hydrophilized.

For example, in the third processing block G3, as shown in FIG. 2, thetransition devices 50 and 51 for the wafers W_(U) and W_(L) and thelaminated wafer W_(T) are provided in two stages sequentially from thebottom.

As shown in FIG. 1, a wafer transfer zone 60 is formed in a regionsurrounded by the first processing block G1 to the third processingblock G3. In the wafer transfer zone 60, for example, a wafer transferdevice 61 is arranged.

The wafer transfer device 61 includes a transfer arm that is movable,for example, in the vertical direction and the horizontal direction (theY-direction and the X-direction) and rotatable about the vertical axis.The wafer transfer apparatus 61 moves within the wafer transfer zone 60and can transfer the wafers W_(U) and W_(L) and the laminated waferW_(T) to predetermined apparatuses in the first processing block G1, thesecond processing block G2 and the third processing block G3.

In the above-described bonding system 1, a control part 70 is providedas shown in FIG. 1. The control part 70 is, for example, a computer, andincludes a program storage part (not shown). In the program storagepart, there is stored a program for controlling the process of thewafers W_(U) and W_(L) and the laminated wafer W_(T) in the bondingsystem 1. The program storage part also stores a program for controllingthe operations of driving systems of the above-described variousprocessing apparatuses, the transfer devices and the like to realize awafer bonding process (to be described later) in the bonding system 1.The programs described above are recorded on a computer-readable storagemedium H such as a computer-readable hard disk (HD), a flexible disk(FD), a compact disk (CD), a magneto-optical disk (MO), a memory card orthe like and may be installed in the control part 70 from the storagemedium H.

2. Configuration of Bonding Apparatus

Next, the configuration of the above-described bonding apparatus 41 willbe described.

<2-1. Overall Configuration of Bonding Apparatus>

As shown in FIGS. 4 and 5, the bonding apparatus 41 includes aprocessing container 100, the interior of which is hermeticallysealable. A loading/unloading port 101 through which the wafers W_(U)and W_(L) and the laminated wafer W_(T) are transferred, is formed inthe lateral surface of the processing container 100 at the side of thewafer transfer zone 60. An opening/closing shutter 102 is provided inthe loading/unloading port 101.

The inside of the processing container 100 is partitioned into atransfer region T1 and a process region T2 by an inner wall 103. Theloading/unloading port 101 described above is formed in the lateralsurface of the processing container 100 in the transfer region T1. Inaddition, a loading/unloading port 104 through which the wafers W_(U)and W_(L) and the laminated wafer W_(T) are transferred, is also formedin the inner wall 103.

A transition 110 for temporarily mounding the wafers W_(U) and W_(L) andthe laminated wafer W_(T) thereon is provided in the positiveY-direction of the transfer region T1. The transition 110 is formed in,for example, two stages and is capable of simultaneously mounting anytwo of the wafers W_(U) and W_(L) and the laminated wafer W_(T) thereon.

In the transfer region T1, a wafer transfer mechanism 111 is provided.The wafer transfer mechanism 111 includes a transfer arm that ismovable, for example, in the vertical direction and the horizontaldirection (the X-direction and Y-direction) and rotatable about thevertical axis. The wafer transfer mechanism 111 can transfer the wafersW_(U) and W_(L) and the laminated wafer W_(T) inside the transfer regionT1 or between the transfer region T1 and the process region T2.

A position adjustment mechanism 120 for adjusting the horizontalorientation of the wafer W_(U) or W_(L) is provided in the negativeY-direction of the transfer region T1. The position adjustment mechanism120 includes a base 121 provided with a holding part (not shown) forholding and rotating the wafer W_(U) or W_(L), and a detection part 122for detecting the position of a notch portion of the wafer W_(U) orW_(L). The position adjusting mechanism 120 detects the position of thenotch portion of the wafer W_(U) or W_(L) by the detection part 122while rotating the wafer W_(U) or W_(L) held on the base 121, wherebythe position of the notch portion is adjusted to adjust the horizontalorientation of the wafer W_(U) or W_(L). The structure for holding thewafer W_(U) or W_(L) on the base 121 is not particularly limited.Various structures such as, for example, a pin chuck structure and aspin chuck structure may be used.

In the transfer region T1, an inverting mechanism 130 for inverting thefront and back surfaces of the upper wafer W_(U) is provided. Theinverting mechanism 130 includes a holding arm 131 for holding the upperwafer W_(U). The holding arm 131 extends in the horizontal direction(the X-direction). In addition, in the holding arm 131, holding members132 for holding the upper wafer W_(U) are provided at, for example, fourlocations.

The holding arm 131 is supported by a driving part 133 including, forexample, a motor or the like. The holding arm 131 is rotatable about ahorizontal axis by the driving part 133. Furthermore, the holding arm131 is rotatable about the driving part 133 and is movable in thehorizontal direction (the X-direction). Below the driving part 133,another driving part (not shown) including, for example, a motor or thelike is provided. This other driving part allows the driving part 133 tomove in the vertical direction along a support column 134 extending inthe vertical direction. In this way, the upper wafer W_(U) held by theholding members 132 can be rotated about the horizontal axis and can bemoved in the vertical direction and the horizontal direction by thedriving part 133. In addition, the upper wafer W_(U) held by the holdingmembers 132 can rotate about the driving part 133 and can move betweenthe position adjustment mechanism 120 and an upper chuck 140 describedlater.

In the process region T2, there are provided an upper chuck 140 as afirst holding part for adsorptively holding the upper wafer W_(U) on thelower surface thereof, and a lower chuck 141 as a second holding partfor adsorptively holding the lower wafer W_(L) mounted on the uppersurface thereof. The lower chuck 141 is provided below the upper chuck140 and is disposed to face the upper chuck 140. In other words, theupper wafer W_(U) held by the upper chuck 140 and the lower wafer W_(L)held by the lower chuck 141 can be arranged to face each other.

The upper chuck 140 is held by an upper chuck holding part 150 providedabove the upper chuck 140. The upper chuck holding part 150 is providedon a ceiling surface of the processing container 100. In other words,the upper chuck 140 is fixed to the processing container 100 via theupper chuck holding part 150.

In the upper chuck holding part 150, there is provided an upper imagingpart 151 configured to image the surface W_(L1) of the lower wafer W_(L)held by the lower chuck 141. In other words, the upper imaging part 151is provided adjacent to the upper chuck 140. For example, a CCD camerais used as the upper imaging part 151.

The lower chuck 141 is supported by a lower chuck stage 160 providedbelow the lower chuck 141. In the lower chuck stage 160, there isprovided a lower imaging part 161 configured to image the surface W_(U1)of the upper wafer W_(U) held by the upper chuck 140. In other words,the lower imaging part 161 is provided adjacent to the lower chuck 141.For example, a CCD camera is used as the lower imaging part 161.

The lower chuck stage 160 is supported by a first lower chuck movingpart 162 provided below the lower chuck stage 160. The first lower chuckmoving part 162 is supported by a support base 163. The first lowerchuck moving part 162 is configured to move the lower chuck 141 in thehorizontal direction (the X-direction) as described later. Furthermore,the first lower chuck moving part 162 is configured to move the lowerchuck 141 in the vertical direction and to rotate the lower chuck 141about the vertical axis.

The support base 163 is attached to a pair of rails 164 and 164 providedat the lower surface side of the support base 163 and extending in thehorizontal direction (the X-direction). The support base 163 isconfigured to move along the pair of rails 164 by the first lower chuckmoving part 162. The first lower chuck moving part 162 is moved by, forexample, a linear motor (not shown) provided along the rails 164.

The rails 164 and 164 are disposed in a second lower chuck moving part165. The second lower chuck moving part 165 is attached to a pair ofrails 166 and 166 provided at the lower surface side of the second lowerchuck moving part 165 and extending in the horizontal direction (theY-direction). The second lower chuck moving part 165 is configured tomove along the rails 166. That is to say, the second lower chuck movingpart 165 is configured to move the lower chuck 141 in the horizontaldirection (the Y-direction). The second lower chuck moving part 165 ismoved by, for example, a linear motor (not shown) provided along therails 166. The rails 166 and 166 are disposed on a mounting table 167provided on the bottom surface of the processing container 100.

<2-2. Configuration of Upper Chuck>

Next, a detailed configuration of the upper chuck 140 of the bondingapparatus 41 will be described.

As shown in FIGS. 6 and 7, a pin chuck system is used as the upper chuck140. The upper chuck 140 includes a main body part 170 having a diameterequal to or larger than a diameter of the upper wafer W_(U) in a planview. A plurality of pins 171 for making contact with the back surfaceW_(U2) of the upper wafer W_(U) is provided on the lower surface of themain body part 170. In FIG. 7, the illustration of the pins 171 isomitted.

A plurality of suction portions 172 to 174 for vacuum-drawing andadsorbing the upper wafer W_(U) is provided on the lower surface of themain body part 170. The suction portions 172 to 174 have the same heightas the pins 171 and make contact with the back surface W_(U2) of theupper wafer W_(U).

The first suction portions 172 have an arc shape in a plan view. Aplurality of, for example, eight, first suction portions 172 arearranged side by side in an outer peripheral portion of the main bodypart 170 in a concentric relationship with the main body part 170 atpredetermined intervals in the circumferential direction.

A first vacuum pump 172 b is connected to each of the eight firstsuction portions 172 via first suction pipes 172 a, respectively. By thevacuum-drawing performed by the first vacuum pump 172 b, the eight firstsuction portions 172 can individually suck the upper wafer W_(U).

Similar to the first suction portions 172, the second suction portions173 have an arc shape in a plan view. A plurality of, for example,eight, second suction portions 173 are arranged side by side at theinner peripheral side of the main body part 170 inward of the firstsuction portions 172 in a concentric relationship with the main bodypart 170 at predetermined intervals in the circumferential direction.Central portions of the first suction portions 172 and central portionsof the second suction portions 173 are disposed on the central line ofthe main body part 170.

A second vacuum pump 173 b is connected to each of the eight secondsuction portions 173 via second suction pipes 173 a, respectively. Byvacuum-drawing performed by the second vacuum pump 173 b, the eightsecond suction portions 173 can individually suck the upper wafer W_(U).

The third suction portion 174 has an annular shape in a plan view. Thethird suction portion 174 is disposed at the inner peripheral side ofthe main body part 170 inward of the second suction portions 173 in aconcentric relationship with the main body part 170. A third vacuum pump174 b is connected to the third suction portion 174 via third suctionpipes 174 a. By the vacuum-drawing performed by the third vacuum pump174 b, the third suction portion 174 can suck the upper wafer W_(U).

In the main body part 170, there are provided sensors 175 as substratedetection parts for detecting the detachment of the upper wafer W_(U)from the main body part 170. A plurality of, for example, eight, sensors175 are arranged side by side between the first suction portions 172 andthe second suction portions 173 in a concentric relationship with themain body part 170 at predetermined intervals in the circumferentialdirection. That is to say, central portions of the sensors 175, thecentral portions of the first suction portions 172 and the centralportions of the second suction portions 173 are disposed on the centralline of the main body part 170. Details of the type and arrangement ofthe sensors 175 will be described later.

A through-hole 176 penetrating the main body part 170 in the thicknessdirection is formed in the central portion of the main body part 170.The central portion of the main body part 170 corresponds to the centralportion of the upper wafer W_(U) adsorptively held by the upper chuck140. A leading end portion of an actuator part 191 of a pressing member190, which will be described later, is inserted through the through-hole176.

<2-3. Details of Sensor of Upper Chuck>

Next, the details of the above-described sensors 175 and a controlmethod of the suction portions 172 to 174 using the inspection resultsof the sensors 175 will be described.

When bonding the upper wafer W_(U) and the lower wafer W_(L) as will bedescribed later, first, the central portion of the upper wafer W_(U) ispushed down and brought into contact with the central portion of thelower wafer W_(L). The central portion of the upper wafer W_(U) and thecentral portion of the lower wafer W_(L) are bonded by virtue of anintermolecular force, whereby a bonding area is formed in the centralportions of both wafers. Thereafter, a bonding wave is generated suchthat the bonding area expands from the central portions of both wafersW_(U) and W_(L) toward the outer peripheral portions thereof. Thus, thefront surfaces W_(U1) and W_(L1) of the upper wafer W_(U) and the lowerwafer W_(L) are bonded to each other over the entire surfaces.

The sensors 175 are provided in the main body part 170 in order to graspthe bonding wave.

Various sensors may be used as the sensors 175. For example, reflectiontype fiber sensors may be used as the sensors 175. In such a case, lightis emitted from the sensors 175 toward the upper wafer W_(U), and thereflected light is received by the sensors 175 to measure a receivedlight amount. By measuring the reception amount of the reflected light,it is possible to grasp the degree of orthogonality between the opticalaxis and the upper wafer W_(U). That is to say, when the amount ofreflected light is small, the degree of orthogonality between theoptical axis and the upper wafer W_(U) is large (the inclination of theupper wafer W_(U) is large). This means that the upper wafer W_(U) isdetached from the upper chuck 140 and is not in contact with the lowerwafer W_(L). On the other hand, when the amount of reflected light islarge, the degree of orthogonality between the optical axis and theupper wafer W_(U) is small (the inclination of the upper wafer W_(U) issmall). This means that the upper wafer W_(U) is detached from the upperchuck 140 and is in contact with the lower wafer W_(L). Therefore, bymeasuring the reflected light amount with the sensors 175, it ispossible to detect the contact state of the upper wafer W_(U) and thelower wafer W_(L) in the sensors 175 (in other words, the state of thedetachment of the upper wafer W_(U) from the upper chuck 140). Thismakes it possible to grasp the bonding wave.

For example, electrostatic capacitance sensors or distance measurementsensors may be used as the sensors 175. In the case of using theelectrostatic capacitance sensors, the distance between the upper chuck140 and the upper wafer W_(U) can be measured by measuring theelectrostatic capacitance with the upper wafer W_(U). In the case ofusing the distance measurement sensors, the distance between the upperchuck 140 and the upper wafer W_(U) can be measured by emitting a laserbeam from the sensors 175 toward the upper wafer W_(U) and receiving thereflected light by the sensors 175. By measuring the distance betweenthe upper chuck 140 and the upper wafer W_(U) in this manner, it ispossible to detect the contact state between the upper wafer W_(U) andthe lower wafer W_(L) in the sensors 175 (in other words, the state ofthe detachment of the upper wafer W_(U) from the upper chuck 140). Thismakes it possible to grasp the bonding wave.

For example, fluid sensors may be used as the sensors 175. In this case,adsorbing pads (not shown) are provided in the main body part 170. Thatis to say, the adsorbing pads may be provided at the positions ofreference numeral “175” shown in FIGS. 6 and 7, and the sensors 175 maybe provided in suction pipes (not shown) connected to the respectiveadsorbing pads. The adsorbing pads are not intended to adsorptively holdthe upper wafer W_(U), but are configured to vacuum-draw the upper waferW_(U) with a very low pressure, for example, about −10 kPa, that doesnot affect the bonding wave. The sensors 175 measure a flow rate orpressure of a gas flowing through the respective suction pipes. Forexample, when the upper wafer W_(U) is detached from the upper chuck140, the flow of the gas inside the suction pipes is changed, and theflow rate and pressure of the gas is changed. The sensors 175 canmeasure the change in gas flow inside the suction pipes and can detectthe detachment of the upper wafer W_(U) from the upper chuck 140 (inother words, the contact state between the upper wafer W_(U) and thelower wafer W_(L)). This makes it possible to grasp the bonding wave.The sensor 175 may be provided in the first suction pipes 172 a of thefirst suction portions 172 and the second suction pipes 173 a of thesecond suction portions 173, respectively.

As described above, the sensors 175 are disposed side by side betweenthe first suction portions 172 and the second suction portions 173 in aconcentric relationship with the main body part 170 at predeterminedintervals in the circumferential direction. Next, the arrangement of thesensors 175 will be described.

The arrangement of the sensors 175 is determined according to thephysical properties of the upper wafer W_(U), for example, theanisotropy such as Young's modulus and Poisson's ratio. FIG. 8 is anexplanatory view showing a state of expansion of a bonding area betweenwafers in the related art. The present inventors have found that asshown in FIG. 8, the bonding area A is not concentrically expanded butis non-uniformly expanded when performing a bonding process. FIG. 8 is aplan view of the upper wafer W_(U) held by the upper chuck 140 as viewedfrom below.

The upper wafer W_(U) is a monocrystalline silicon wafer having acrystal direction of [100] in a direction perpendicular to the frontsurface W_(U1). The notch portion N of the upper wafer W_(U) is formedin the outer edge of the upper wafer W_(U) in a [011] crystal direction.The bonding area A is more rapidly expanded in directions of a 45°period (directions of 45°, 135°, 225° and 315° shown in FIG. 8)(hereinafter sometimes referred to as “45° directions”) with referenceto a direction oriented in a [010] crystal direction parallel to thefront surface W_(U1) of the upper wafer W_(U), from the central portionof the upper wafer W_(U), rather than in directions of a 90° period(directions of 0°, 90°, 180° and 270° shown in FIG. 8) (hereinaftersometimes referred to as “90° directions”) with reference to a directionoriented in a [0-11] crystal direction parallel to the front surfaceW_(U1) of the upper wafer W_(U), from the central portion of the upperwafer W_(U). As a result, the shape of the bonding area A, which wascircular at the start of bonding (central portion bonding), is gettingclose to a quadrangle having vertices located in the 45° directions asthe bonding area A is expanded.

In the present embodiment, the eight sensors 175 are provided in aconcentric relationship with the main body part 170. That is to say, thesensors 175 are provided in the 90° directions and the 45° directions.Therefore, by detecting the detachment of the upper wafer W_(U) from theupper chuck 140 with the sensors 175 and detecting the bonding area Ashown in FIG. 8, it is possible to grasp the bonding wave.

The detection results of the sensors 175 are outputted to the controlpart 70. The control part 70 controls the operations of the suctionportions 172 to 174 based on the detection results of the sensors 175.

FIGS. 9A and 9B are graphs showing examples of the detection result ofthe sensors 175. The horizontal axis in FIGS. 9A and 9B represents theelapsed time of the bonding process, and the vertical axis representsthe output result of the sensors 175, namely the position of the upperwafer W_(U) relative to the upper chuck 140. When the detection resultof the sensors 175 is P1 (when the upper wafer W_(U) is close to theupper chuck 140), the upper wafer W_(U) is in contact with the upperchuck 140 at the positions of the sensors 175, and the bonding area A isnot reached. When the detection result of the sensors 175 is P2 (whenthe upper wafer W_(U) is far from the upper chuck 140), the upper waferW_(U) is separated from the upper chuck 140 at the positions of thesensors 175 and is in contact with the lower wafer W_(L). Thus, thebonding area A is reached.

FIG. 9A shows a case where the bonding area A is uneven and is expandedin a substantially quadrangular shape as shown in FIG. 8. As describedabove, the bonding area A is expanded faster in the 45° directions thanin the 90° directions. Therefore, a time difference ΔT between thetiming when the bonding area A is reached in the 45° directions and thetiming when the bonding area A is reached in the 90° directionsincreases.

Therefore, in order to make the expansion of the bonding area A uniform,the control part 70 performs control so that the time difference ΔTfalls within a predetermined threshold value as shown in FIG. 9B. Thereis a correlation between the time difference ΔT and the distortion ofthe laminated wafer W_(T) after bonding. The predetermined thresholdvalue of ΔT is set from the allowable range of distortion of thelaminated wafer W_(T).

Specifically, the control of the control part 70 includes delaying thetiming at which the second suction portions 173 release the upper waferW_(U) in the 45° directions, and advancing the timing at which thesecond suction portions 173 release the upper wafer W_(U) in the 90°directions. Thus, at the positions of the eight sensors 175, the timingsat which the bonding area A is reached can be made substantially thesame. Therefore, it is possible to make the expansion of the bondingarea A uniform and to make the bonding wave (nearly concentric shape)uniform.

In the present embodiment, the case where the suction timing of thesecond suction portions 173 is controlled based on the detection resultof the sensors 175 has been described. However, the suction force of thesecond suction portions 173 may be further controlled. In addition,other suction portions 172 and 174 may be controlled based on thedetection result of the sensors 175.

<2-4. Configuration of Upper Chuck Holding Part>

Next, a detailed configuration of the upper chuck holding part 150 ofthe bonding apparatus 41 will be described.

As shown in FIG. 5, the upper chuck holding part 150 includes an upperchuck stage 180 provided on the upper surface of the main body part 170of the upper chuck 140. The upper chuck stage 180 is provided so as tocover at least the upper surface of the main body part 170 in a planview and is fixed to the main body part 170 by, for example, screws. Theupper chuck stage 180 is supported by a plurality of support members 181provided on the ceiling surface of the processing container 100.

On the upper surface of the upper chuck stage 180, as shown in FIG. 6,the pressing member 190 for pressing the central portion of the upperwafer W_(U) is further provided. The pressing member 190 includes theactuator part 191 and a cylinder part 192.

The actuator part 191 generates a constant pressure in a certaindirection using the air supplied from an electro-pneumatic regulator(not shown). Thus, the pressure can be generated constantly regardlessof a position to which the pressure is applied. By the air supplied fromthe electro-pneumatic regulator, the actuator part 191 can make contactwith the central portion of the upper wafer W_(U) and can control apress load to be applied to the central portion of the upper waferW_(U). In addition, the leading end portion of the actuator part 191 canbe moved up and down in the vertical direction through the through-hole176 by the air supplied from the electro-pneumatic regulator.

The actuator part 191 is supported by the cylinder part 192. Thecylinder part 192 can move the actuator part 191 in the verticaldirection using, for example, a driving part that incorporates a motor.

As described above, the pressing member 190 controls the press loadusing the actuator part 191 and controls the movement of the actuatorpart 191 using the cylinder part 192. At the time of bonding the wafersW_(U) and W_(L) to be described later, the pressing member 190 can bringthe central portion of the upper wafer W_(U) and the central portion ofthe lower wafer W_(L) into contact with each other and can press themagainst each other.

<2-5. Configuration of Lower Chuck>

Next, a detailed configuration of the lower chuck 141 of the bondingapparatus 41 will be described.

As shown in FIG. 6, the lower chuck 141 adopts a pin chuck system justlike the upper chuck 140. The lower chuck 141 includes a main body part200 having a diameter equal to or larger than a diameter of the lowerwafer W_(L) in a plan view. On the upper surface of the main body part200, there is provided a plurality of pins 201 that makes contact withthe back surface W_(L2) of the lower wafer W_(L). An outer rib 202having the same height as the pins 201 and supporting an outerperipheral portion of the back surface W_(L2) of the lower wafer W_(L)is provided on an outer peripheral portion of the upper surface of themain body part 200. The outer rib 202 is annularly provided outside theplurality of pins 201.

On the upper surface of the main body part 200, an inner rib 203 havingthe same height as the pins 201 and supporting the back surface W_(L2)of the lower wafer W_(L) is provided inward of the outer rib 202. Theinner rib 203 is annularly provided in a concentric relationship withthe outer rib 202. An inner region 204 of the outer rib 202 (hereinaftersometimes referred to as “suction region 204”) is partitioned into afirst suction region 204 a defined inward of the inner rib 203 and asecond suction region 204 b defined outward of the inner rib 203.

In the upper surface of the main body part 200, a first suction port 205a for vacuum-drawing the lower wafer W_(L) is formed in the firstsuction region 204 a. The first suction port 205 a is formed, forexample, at one location in the first suction region 204 a. A firstsuction pipe 206 a provided inside the main body part 200 is connectedto the first suction port 205 a. A first vacuum pump 207 a is connectedto the first suction pipe 206 a.

In the upper surface of the main body part 200, second suction ports 205b for vacuum-drawing the lower wafer W_(L) are formed in the secondsuction region 204 b. The second suction ports 205 b are formed, forexample, at two locations in the second suction region 204 b. Secondsuction pipes 206 b provided inside the main body part 200 are connectedto the second suction ports 205 b. A second vacuum pump 207 b isconnected to the second suction pipes 206 b.

The suction regions 204 a and 204 b surrounded by the lower wafer W_(L),the main body part 200 and the outer rib 202 are vacuum-drawn from thesuction ports 205 a and 205 b, respectively, whereby pressures of thesuction regions 204 a and 204 b are reduced. At this time, theatmosphere outside the suction regions 204 a and 204 b is kept atatmospheric pressure. Therefore, the lower wafer W_(L) is pushed towardthe suction regions 204 a and 204 b by the atmospheric pressure just asmuch as the reduced pressures. Thus, the lower wafer W_(L) isadsorptively held by the lower chuck 141. In addition, the lower chuck141 is configured to be able to vacuum-draw the lower wafer W_(L) foreach of the first suction region 204 a and the second suction region 204b.

In the lower chuck 141, through-holes (not shown) penetrating the mainbody part 200 in the thickness direction are formed, for example, atthree locations, near the central portion of the main body part 200.Lift pins provided under the first lower chuck moving part 162 areinserted through the through-holes.

In the outer peripheral portion of the main body part 200, there areprovided guide members (not shown) that prevent the wafers W_(U) andW_(L) and the laminated wafer W_(T) from jumping out or sliding downfrom the lower chuck 141. The guide members are provided at a pluralityof (for example, four) locations, in the outer peripheral portion of themain body part 200 at equal intervals.

The operations of the respective parts in the bonding apparatus 41 arecontrolled by the control part 70 described above.

3. Bonding Method

Next, a bonding method of the wafers W_(U) and W_(L) performed using thebonding system 1 configured as above will be described. FIG. 10 is aflowchart showing an example of main steps of a wafer bonding process.

First, a cassette C_(U) accommodating a plurality of upper wafers W_(U),a cassette C_(L) accommodating a plurality of lower wafers W_(L) and anempty cassette C_(T) are mounted on predetermined cassette mountingplates 11 of the loading/unloading station 2. Thereafter, the upperwafer W_(U) accommodated in the cassette C_(U) is taken out by the wafertransfer device 22 and is transferred to the transition device 50 of thethird processing block G3 of the processing station 3.

Subsequently, the upper wafer W_(U) is transferred to the surfacemodifying apparatus 30 of the first processing block G1 by the wafertransfer device 61. In the surface modifying apparatus 30, an oxygen gasor a nitrogen gas, which is a processing gas, is excited,plasma-plasmarized and ionized under a predetermined reduced-pressureatmosphere. The oxygen ion or the nitrogen ion is irradiated onto thefront surface W_(U1) of the upper wafer W_(U), whereby the front surfaceW_(U1) is plasma-processed. Thus, the front surface W_(U1) of the upperwafer W_(U) is modified (step S1 in FIG. 10).

Subsequently, the upper wafer W_(U) is transferred to the surfacehydrophilizing apparatus 40 of the second processing block G2 by thewafer transfer device 61. In the surface hydrophilizing apparatus 40,pure water is supplied onto the upper wafer W_(U) while rotating theupper wafer W_(U) held by the spin chuck. Then, the supplied pure wateris diffused on the front surface W_(U1) of the upper wafer W_(U). Thus,hydroxyl groups (silanol groups) adhere to the front surface W_(U1) ofthe upper wafer W_(U) modified in the surface modifying apparatus 30,whereby the front surface W_(U1) is hydrophilized. In addition, thefront surface W_(U1) of the upper wafer W_(U) is cleaned by the purewater (step S2 in FIG. 10).

Subsequently, the upper wafer W_(U) is transferred to the bondingapparatus 41 of the second processing block G2 by the wafer transferdevice 61. The upper wafer W_(U) loaded into the bonding apparatus 41 istransferred to the position adjustment mechanism 120 by the wafertransfer mechanism 111 via the transition 110. Then, the horizontalorientation of the upper wafer W_(U) is adjusted by the positionadjustment mechanism 120 (step S3 in FIG. 10).

Thereafter, the upper wafer W_(U) is delivered from the positionadjustment mechanism 120 to the holding arm 131 of the invertingmechanism 130. Subsequently, in the transfer region T1, the holding arm131 is inverted so that the front and back surfaces of the upper waferW_(U) are inverted (step S4 in FIG. 10). That is to say, the frontsurface W_(U1) of the upper wafer W_(U) is oriented downward.

Thereafter, the holding arm 131 of the inverting mechanism 130 rotatesabout the driving part 133 and moves below the upper chuck 140. Then,the upper wafer W_(U) is delivered from the inverting mechanism 130 tothe upper chuck 140. The back surface W_(U2) of the upper wafer W_(U) isadsorptively held by the upper chuck 140 (step S5 in FIG. 10).Specifically, the vacuum pumps 172 b, 173 b and 174 b are operated tovacuum-draw the upper wafer W_(U) with the suction portions 172, 173 and174, whereby the upper wafer W_(U) is adsorptively held by the upperchuck 140.

While the processes of the above steps S1 to S5 are performed on theupper wafer W_(U), the process for the lower wafer W_(L) is performedfollowing the upper wafer W_(U). First, the lower wafer W_(L)accommodated in the cassette C_(L) is taken out by the wafer transferdevice 22 and is transferred to the transition device 50 of theprocessing station 3.

Subsequently, by the wafer transfer apparatus 61, the lower wafer W_(L)is transferred to the surface modifying apparatus 30 where the frontsurface W_(L1) of the lower wafer W_(L) is modified (step S6 in FIG.10). In step S6, the front surface W_(L1) of the lower wafer W_(L) ismodified in the same manner as in the above-described step S1.

Thereafter, by the wafer transfer device 61, the lower wafer W_(L) istransferred to the surface hydrophilizing apparatus 40 where the frontsurface W_(L1) of the lower wafer W_(L) is hydrophilized and cleaned(step S7 in FIG. 10). In step S7, the front surface WL₁ of the lowerwafer WL is hydrophilized and cleaned in the same manner as in theabove-described step S2.

Thereafter, the lower wafer W_(L) is transferred to the bondingapparatus 41 by the wafer transfer device 61. The lower wafer W_(L)loaded into the bonding apparatus 41 is transferred to the positionadjustment mechanism 120 by the wafer transfer mechanism via thetransition 110. Then, the horizontal orientation of the lower waferW_(L) is adjusted by the position adjustment mechanism 120 (step S8 inFIG. 10).

Thereafter, the lower wafer W_(L) is transferred to the lower chuck 141by the wafer transfer mechanism 111, and the back surface W_(L2) of thelower wafer W_(L) is adsorptively held by the lower chuck 141 (step S9in FIG. 10). Specifically, the vacuum pumps 207 a and 207 b are operatedto vacuum-draw the lower wafer W_(L) via the suction ports 205 a and 205b in the suction regions 204 a and 204 b, whereby the lower wafer W_(L)is adsorptively held by the lower chuck 141.

Subsequently, the horizontal positions of the upper wafer W_(U) held bythe upper chuck 140 and the lower wafer W_(L) held by the lower chuck141 are adjusted. Specifically, the lower chuck 141 is moved in thehorizontal direction (the X-direction and the Y-direction) by the firstlower chuck moving part 162 and the second lower chuck moving part 165,and predetermined reference points on the front surface W_(L1) of thelower wafer W_(L) are sequentially imaged using the upper imaging part151. At the same time, predetermined reference points on the frontsurface W_(U1) of the upper wafer W_(U) are sequentially imaged usingthe lower imaging part 161. The images thus captured are outputted tothe control part 70. Based on the image captured by the upper imagingpart 151 and the image captured by the lower imaging part 161, thecontrol part 70 controls the first lower chuck moving part 162 and thesecond lower chuck moving part 165 to move the lower chuck 141 to aposition where the reference points of the upper wafer W_(U) and thereference points of the lower wafer W_(L) are respectively aligned withone another. In this way, the horizontal positions of the upper waferW_(U) and the lower wafer W_(L) are adjusted (step S10 in FIG. 10).

In step S10, as described above, the lower chuck 141 is moved in thehorizontal direction, and is also rotated by the first lower chuckmoving part 162, whereby the rotational direction position of the lowerchuck 141 (the orientation of the lower chuck 141) is also adjusted.

Thereafter, the lower chuck 141 is vertically moved upward by the firstlower chuck moving part 162, and the vertical positions of the upperchuck 140 and the lower chuck 141 are adjusted to adjust the verticalpositions of the upper wafer W_(U) held by the upper chuck 140 and thelower wafer W_(L) held by the lower chuck 141 (step S11 in FIG. 10). Thedistance between the front surface W_(L1) of the lower wafer W_(L) andthe front surface W_(U1) of the upper wafer W_(U) is adjusted to apredetermined distance, for example, 50 to 200 μm. Thus, as shown inFIG. 11, the upper wafer W_(U) and the lower wafer W_(L) are aligned toface each other at predetermined positions.

Subsequently, the bonding process of the upper wafer W_(U) held by theupper chuck 140 and the lower wafer W_(L) held by the lower chuck 141 isperformed.

In the present embodiment, descriptions will be made on a case where thesuction timing of the second suction parts 173 is set in advance so thatthe bonding wave becomes uniform as described above. That is to say, forexample, the expansion of the bonding area A is detected by the sensors175 with respect to the upper wafers W_(U) of the previous lot. Based onthe detection result, the suction timing of the second suction parts 173with respect to the upper wafer W_(U) of the current lot is set.

First, as shown in FIG. 12, the actuator part 191 is lowered by thecylinder part 192 of the pressing member 190. Then, as the actuator part191 is lowered, the central portion of the upper wafer W_(U) is pressedand lowered. At this time, a predetermined press load is applied to theactuator part 191 by the air supplied from the electro-pneumaticregulator. Then, the central portion of the upper wafer W_(U) and thecentral portion of the lower wafer W_(L) are brought into contact witheach other and pressed against each other by the pressing member 190(step S12 in FIG. 10).

In step S13, the operation of the first vacuum pump 172 b is stopped tostop the vacuum-drawing of the upper wafer W_(U) from the first suctionportions 172. While operating the second vacuum pump 173 b and the thirdvacuum pump 174 b, the upper wafer W_(U) is vacuum-drawn by the secondsuction portions 173 and the third suction portion 174.

If the central portion of the upper wafer W_(U) and the central portionof the lower wafer W_(L) are brought into contact with each other andpressed against each other, bonding is started between the centralportions. That is to say, since the front surface W_(U1) of the upperwafer W_(U) and the front surface W_(L1) of the lower wafer W_(L) havebeen modified in steps S1 and S6, respectively, a van der Waals force(intermolecular force) is first generated between the front surfacesW_(U1) and W_(L1), whereby the front surfaces W_(U1) and W_(L1) arebonded to each other. Furthermore, since the front surface W_(U1) of theupper wafer W_(U) and the front surface W_(L1) of the lower wafer W_(L)have been hydrophilized in steps S2 and S7, respectively, thehydrophilic groups existing between the front surfaces W_(U1) and W_(L1)are hydrogen-bonded (which generates an intermolecular force). Thus, thefront surfaces W_(U1) and W_(L1) are strongly bonded to each other. Inthis way, the bonding area A is formed.

Thereafter, between the upper wafer W_(U) and the lower wafer W_(L), abonding wave is generated in which the bonding area A expands from thecenter portions of the upper wafer W_(U) and the lower wafer W_(L)toward the outer peripheral portions thereof.

The operation of the second vacuum pump 173 b is stopped in a state inwhich the central portion of the upper wafer W_(U) and the centralportion of the lower wafer W_(L) are pressed against each other by thepressing member 190 as shown in FIG. 13. Thus, the vacuum-drawing of theupper wafer W_(U) from the second suction portions 173 is stopped. Atthis time, as described above, the suction timings of the eight secondsuction portions 173 are made different. That is to say, the timing atwhich the second suction portions 173 release the upper wafer W_(U) inthe 45° directions is delayed, and the timing at which the secondsuction portions 173 release the upper wafer W_(U) in the 90° directionsis advanced. As a result, at the positions of the eight sensors 175, thetimings at which the bonding area A is reached can be made substantiallythe same. This makes the bonding wave uniform.

As shown in FIG. 14, the operation of the third vacuum pump 174 b isstopped, and the vacuum-drawing of the upper wafer W_(U) from the thirdsuction portion 174 is stopped. Then, the upper wafer W_(U) sequentiallydrops onto the lower wafer W_(L) and comes into contact with the lowerwafer W_(L). The bonding between the front surfaces W_(U1) and W_(L1) bya van der Waals and a hydrogen bond is successively expanded. In thisway, the front surface W_(U1) of the upper wafer W_(U) and the frontsurface W_(L1) of the lower wafer W_(L) are brought into contact witheach other over the entire surfaces, whereby the upper wafer W_(U) andthe lower wafer W_(L) are bonded (step S13 in FIG. 10). At this time,the bonding wave becomes uniform. It is therefore possible to suppressthe distortion of the laminated wafer W_(T).

In step S13, the bonding area A is detected using the eight sensors 175,the bonding wave is monitored to inspect the bonding state between theupper wafer W_(U) and the lower wafer W_(L). As described above, in thepresent embodiment, the suction timings of the second suction portions173 are set in advance so that the bonding wave becomes uniform.However, there may be a case where the bonding wave becomes non-uniformdue to various disturbances. In such a case, an alarm is triggered,which makes it possible to improve the yield of products. In addition,if the bonding wave becomes non-uniform as described above, the suctiontimings of the second suction portions 173 when bonding the subsequentupper wafer W_(U) and the subsequent lower wafer W_(L) are correctedbased on the detection result of the sensors 175.

Thereafter, as shown in FIG. 15, the actuator part 191 of the pressingmember 190 is raised up to the upper chuck 140. Furthermore, theoperations of the vacuum pumps 207 a and 207 b are stopped, thevacuum-drawing of the lower wafer W_(L) in the suction region 204 isstopped so that the adsorptive holding of the lower wafer W_(L) by thelower chuck 141 is stopped.

The laminated wafer W_(T) obtained by bonding the upper wafer W_(U) andthe lower wafer W_(L) is transferred to the transition device 51 by thewafer transfer device 61 and is then transferred to the cassette C_(T)mounted on the predetermined cassette mounting plate 11 by the wafertransfer device 22 of the loading/unloading station 2. In this way, aseries of bonding processes of the wafers W_(U) and W_(L) is completed.

According to the above-described embodiment, the sensors 175 can detectthat the upper wafer W_(U) held by the upper chuck 140 is detached fromthe upper chuck 140. This makes it possible to grasp the bonding wave.Then, the control part 70 controls the suction timings of the secondsuction portions 173 based on the detection result of the sensors 175.As a result, the bonding wave can be made uniform, which makes itpossible to suppress the distortion of the laminated wafer W_(T).

The bonding system 1 according to the present embodiment includes thesurface modifying apparatus 30, the surface hydrophilizing apparatus 40and the bonding apparatus 41. Thus, it is possible to efficiently bondthe wafers W_(U) and W_(L) in a single system. Therefore, it is possibleto improve the throughput of the wafer bonding process.

4. Other Embodiments

Next, other embodiments of the present disclosure will be described.

In the upper chuck 140 according to the above embodiment, the sensors175 have been described to be disposed side by side between the firstsuction portions 172 and the second suction portions 173 in a concentricrelationship with the main body part 170 at predetermined intervals inthe circumferential direction. However, the arrangement of the sensors175 is not limited thereto.

As shown in FIG. 16, in addition to the sensors 175 provided between thefirst suction portions 172 and the second suction portions 173, aplurality of, for example, eight, sensors 175 may be arranged side byside at the inner peripheral side of the main body part 170 inward ofthe second suction portions 173 in a concentric relationship with themain body part 170 at predetermined intervals in the circumferentialdirection. That is to say, one set of paired sensors 175, the centralportion of the first suction portion 172 and the central portion of thesecond suction portion 173 are arranged along the central line of themain body part 170. In the following description, the sensors 175arranged between the first suction portions 172 and the second suctionportions 173 are referred to as “sensors 175 a”. The sensors 175arranged at the inner peripheral side of the second suction portions 173are referred to as “sensors 175 b”.

In this case, the suction timings of the second suction portions 173lying on the same central line as the sensors 175 b can be controlledbased on the detection result of the sensors 175 b. Accordingly, it ispossible to perform feed-forward control of the second suction portions173 in real time and to make the bonding wave uniform in a more reliablemanner.

In some embodiments, the sensors 175 a may be omitted and only thesensors 175 b may be provided. However, since the sensor 175 a aredisposed away from the central portion of the main body part 170, it ispossible for the sensors 175 a to more reliably grasp the non-uniformexpansion of the bonding area A than the sensors 175 b. Specifically,for example, when the diameter of the upper wafer W_(U) is 300 mm, thesensors 175 a may be arranged beyond the diameter of 240 mm from thecentral portion of the main body part 170.

As shown in FIG. 8, in the related art, the bonding area A is expandedin a substantially quadrilateral shape. Taking into consideration thesymmetry of expansion of the bonding area A, the number of sensors 175may be reduced.

For example, as shown in FIGS. 17A and 17B, two sensors 175 may bearranged in a line on the circumference of the main body part 170. Thatis to say, the sensors 175 may be disposed at least in each of the 45°directions and each of the 90° directions, respectively. In such a case,the sensor 175 disposed in one of the 45° directions may be used toestimate the expansion of the bonding area A in other 45° directions,and the sensor 175 disposed in one of the 90° directions may be used toestimate the expansion of the bonding area A in other 90° directions.

However, if the sensors 175 are provided over the entire circumferenceof the main body part 170 as shown in FIG. 7, it is possible to graspthe size of the gap between the upper wafer W_(U) and the lower waferW_(L). In this regard, the upper wafer W_(U) and the lower wafer W_(L)are not precisely parallel but may be inclined by a minute distance, forexample several μm. In this case, as the distance between the upperwafer W_(U) and the lower wafer W_(L) grows larger, air more easilyescapes to the outside. Thus, the bonding area A expands rapidly. Evenif there is a difference in expansion of the bonding area A, if thesensors 175 are provided on the entire circumference of the main bodypart 170, it is possible to appropriately grasp the bonding wave.

In the above embodiment, the contact state between the upper wafer W_(U)and the lower wafer W_(L) is detected using the sensors 175, therebygrasping the bonding wave. In some embodiments, the displacement of theactuator part 191 may be measured to grasp the bonding wave. As shown inFIG. 19, the pressing member 190 is provided with a laser displacementmeter 300. The laser displacement meter 300 measures the displacement ofa target 301 provided in the actuator part 191, thereby measuring thedisplacement of the actuator part 191.

In such a case, in step S12 (FIG. 12) of the above embodiment, when theactuator part 191 of the pressing member 190 is lowered, thedisplacement of the actuator part 191 is measured by the laserdisplacement meter 300. When the displacement measured by the laserdisplacement meter 300 reaches a predetermined threshold value, it isdetected that the central portion of the upper wafer W_(U) and thecentral portion of the lower wafer W_(L) are in contact with each other.

The start of the bonding area A can be grasped on the basis of themeasurement result obtained by the laser displacement meter 300 in thismanner. It is therefore possible to more appropriately grasp the bondingwave. It is also possible to control the suction timings of the suctionportions 172 to 174 on the basis of the measurement result obtained bythe laser displacement meter 300.

The displacement meter provided in the pressing member 190 is notlimited to the laser displacement meter 300 but may be arbitrarilyselected as long as it can measure the displacement of the actuator part191.

In the upper chuck 140 of the above embodiment, the single second vacuumpump 173 b has been described to be connected to each of the eightsecond suction portions 173. Alternatively, a plurality of second vacuumpumps 173 b may be provided to collectively control the operations ofthe second suction portions 173 on a group basis. For example, a firstgroup of the second suction portions 173 disposed in four 45° directionsmay be controlled by one second vacuum pump 173 b. Furthermore, a secondgroup of the second suction portions 173 disposed in four 90° directionsmay be controlled by other second vacuum pumps 173 b.

Similarly, with respect to the eight first suction portions 172, aplurality of first vacuum pumps 172 b may be provided to collectivelycontrol the operations of the first suction portions 172 on a groupbasis.

The number and arrangement of the suction portions 172 to 174 are notlimited to the example shown in FIG. 7. In the main body part 170, thenumber of suction portions on the same circumference may be a numberother than eight. Furthermore, in the main body part 170, the suctionportions may be provided in three or more rows.

In the bonding apparatus 41 of the above embodiment, the lower chuck 141is configured to be movable in the horizontal direction. However, theupper chuck 140 may be configured to be movable in the horizontaldirection, or both the upper chuck 140 and the lower chuck 141 may beconfigured to be movable in the horizontal direction.

In addition, in the bonding apparatus 41 of the above embodiment, thelower chuck 141 is configured to be movable in the vertical direction.However, the upper chuck 140 may be configured to be movable in thevertical direction, or both the upper chuck 140 and the lower chuck 141may be configured to be movable in the vertical direction.

Furthermore, in the bonding apparatus 41 of the above embodiment, thelower chuck 141 is configured to be rotatable. However, the upper chuck140 may be configured to be rotatable, or both the upper chuck 140 andthe lower chuck 141 may be configured to be rotatable.

In the bonding system 1 of the above embodiment, after the wafers W_(U)and W_(L) are bonded by the bonding apparatus 41, the laminated waferW_(T) obtained by the bonding may be heated (annealed) at apredetermined temperature. By performing such a heat treatment on thelaminated wafer W_(T), it is possible to firmly bond the bondinginterface.

Although the preferred embodiments of the present disclosure have beendescribed above with reference to the accompanying drawings, the presentdisclosure is not limited to such embodiments. It will be apparent tothose skilled in the art that various modifications or changes may beconceived within the scope of the idea described in the claims. It is tobe understood that such modifications or changes naturally fall withinthe technical scope of the present disclosure. The present disclosure isnot limited to these embodiments but may take various forms. The presentdisclosure may also be applied to a case where the substrate is asubstrate other than the wafer, such as an FPD (flat panel display), amask reticle for a photomask or the like.

According to the present disclosure in some embodiments, a substratedetection part can detect that a first substrate held by a first holdingpart is detached from the first holding part. When the first substrateis detached, the first substrate is dropped down and brought intocontact with a second substrate. The first substrate and the secondsubstrate are bonded by virtue of an intermolecular force. Accordingly,by detecting the detachment of the first substrate, it is possible tograsp a bonding wave and to inspect a state of the bonding process ofthe substrates. Further, for example, if the bonding wave is uniform(the state of the bonding process is normal), the bonding process may becontinuously performed. On the other hand, for example, if the bondingwave is non-uniform (the state of the bonding process is abnormal), thebonding process may be performed by correcting a process condition.Therefore, according to the present disclosure, it is possible toappropriately perform the bonding process

According to the present disclosure in some embodiments, it is possibleto inspect a state of a bonding process of substrates and toappropriately perform the bonding process.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosures. Indeed, the embodiments described herein maybe embodied in a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments describedherein may be made without departing from the spirit of the disclosures.The accompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosures.

What is claimed is:
 1. A bonding apparatus for bonding substratestogether, comprising: a first holding part configured to adsorptivelyhold a first substrate by vacuum-drawing the first substrate on a lowersurface of the first substrate; a second holding part provided below thefirst holding part and configured to adsorptively hold a secondsubstrate by vacuum-drawing the second substrate on an upper surface ofthe second substrate; a pressing member provided in the first holdingpart and configured to press a central portion of the first substrate;and a plurality of substrate detection parts provided in the firstholding part and configured to detect a detachment of the firstsubstrate from the first holding part, wherein the plurality ofsubstrate detection parts is arranged in a concentric relationship withthe first holding part and inward of a periphery of the first substrate.2. The bonding apparatus of claim 1, wherein the plurality of substratedetection parts includes reflection type fiber sensors for irradiating alight onto the first substrate and measuring an amount of a reflectedlight from the first substrate.
 3. The bonding apparatus of claim 1,wherein the plurality of substrate detection parts includeselectrostatic capacitance sensors for measuring an electrostaticcapacitance between the substrate detection parts and the firstsubstrate.
 4. The bonding apparatus of claim 1, wherein the plurality ofsubstrate detection parts includes distance measurement sensors toirradiate a laser light onto the first substrate, receive a reflectedlaser light from the first substrate, and measure a distance between thefirst holding part and the first substrate based on the reflected laserlight.
 5. The bonding apparatus of claim 1, wherein the plurality ofsubstrate detection parts is provided along at least one of a pluralityof circumferences in a concentric relationship with the first holdingpart.
 6. The bonding apparatus of claim 1, wherein the first holdingpart includes a plurality of suction portions configured to make contactwith the first substrate and to adsorb the first substrate byvacuum-drawing the first substrate, and the bonding apparatus furthercomprises a controller configured to control the plurality of suctionportions based on a detection result of the plurality of substratedetection parts.
 7. The bonding apparatus of claim 6, wherein thecontroller is configured to calculate, based on the detection result ofthe plurality of substrate detection parts, a time difference between atiming at which one of the plurality of substrate detection partsdetects the detachment of the first substrate and a timing at whichanother of the plurality of substrate detection parts detects thedetachment of the first substrate, and is configured to control theplurality of suction portions so that the time difference falls within apredetermined threshold value.
 8. The bonding apparatus of claim 1,further comprising: a displacement meter configured to measure adisplacement of the pressing member.
 9. A bonding system provided withthe bonding apparatus of claim 1, comprising: a processing stationprovided with the bonding apparatus; and a loading/unloading stationconfigured to hold a plurality of first substrates, a plurality ofsecond substrates or a plurality of laminated substrates each of whichis obtained by bonding the first substrate and the second substrate, andconfigured to load and unload the plurality of first substrates, theplurality of second substrates or the plurality of laminated substratesinto and from the processing station, wherein the processing stationincludes: a surface modifying apparatus configured to modify a surfaceof the first substrate or the second substrate to be bonded; a surfacehydrophilizing apparatus configured to hydrophilize the surface of thefirst substrate or the surface of the second substrate modified by thesurface modifying apparatus; and a transfer device configured totransfer the plurality of first substrates, the plurality of secondsubstrates or the plurality of laminated substrates to the surfacemodifying apparatus, the surface hydrophilizing apparatus and thebonding apparatus, and wherein the bonding apparatus is configured tobond the first substrate and the second substrate whose surfaces arehydrophilized by the surface hydrophilizing apparatus.
 10. A bondingmethod for bonding substrates together, comprising: arranging a firstsubstrate held on a lower surface of a first holding part and a secondsubstrate held on an upper surface of a second holding part so as toface each other; subsequently, lowering a pressing member provided inthe first holding part and configured to press a central portion of thefirst substrate, and causing the pressing member to press and bring thecentral portion of the first substrate and a central portion of thesecond substrate into contact with each other; and subsequently,sequentially bonding the first substrate and the second substrate fromthe central portion of the first substrate toward an outer peripheralportion of the first substrate in a state in which the central portionof the first substrate and the central portion of the second substrateare in contact with each other, wherein the bonding the first substrateand the second substrate includes detecting a detachment of the firstsubstrate from the first holding part and inspecting a state of abonding process, using a plurality of substrate detection parts providedin the first holding part, and wherein the plurality of substratedetection parts is arranged in a concentric relationship with the firstholding part and inward of a periphery of the first substrate.
 11. Thebonding method of claim 10, wherein the plurality of substrate detectionparts are configured to irradiate a light onto the first substrate andto measure a reception amount of a reflected light reflected at thefirst substrate.
 12. The bonding method of claim 10, wherein theplurality of substrate detection parts are configured to measure anelectrostatic capacitance between the plurality of substrate detectionparts and the first substrate.
 13. The bonding method of claim 10,wherein the plurality of substrate detection parts are configured tomeasure a distance between the first holding part and the firstsubstrate.
 14. The bonding method of claim 10, wherein the first holdingpart includes a plurality of suction portions configured to make contactwith the first substrate and to adsorptively hold the first substrate byvacuum-drawing the first substrate, and the plurality of suctionportions is controlled based on detection results of the plurality ofsubstrate detection parts.
 15. The bonding method of claim 14, furtherincluding: calculating a time difference between a timing at which oneof the plurality of substrate detection parts detects the detachment ofthe first substrate and a timing at which another of the plurality ofsubstrate detection parts detects the detachment of the first substrate,and controlling the plurality of suction portions so that the timedifference falls within a predetermined threshold value.
 16. The bondingmethod of claim 10, wherein the bonding the first substrate and thesecond substrate further includes measuring a displacement of thepressing member by a displacement meter, and inspecting a state of abonding process based on a measurement result obtained by thedisplacement meter and detection results obtained by the plurality ofsubstrate detection parts.
 17. A non-transitory computer-readablestorage medium storing a program that operates on a computer of acontrol part configured to control a bonding apparatus so that thebonding method of claim 10 is executed by the bonding apparatus.